PHP package manager
Have you checked Maven for PHP? I've only used Maven in the context of Java applications, but it's certainly:
- Easy to extend – it's really easy to implement Maven plugins
- Manages dependencies – distinguishing compile, test and runtime dependencies (though the compile/runtime distintion doesn't make sense in PHP).
- Repositories are trivial to put up – Apache with mod_dav will give you a working writable repository, but you also have Nexus.
- Distinguishes snapshot from stable artifacts; allows several policies for when to check for new snapshot artifacts and from which repositories get each type.
And many – many – more things.
PEAR2/Pyrus was built for package management for arbitrary applications. I believe it was modeled after the apt/yum architectures.
Helgi - core PEAR member - covers some of it here - http://www.slideshare.net/helgith/pear2-pyrus-the-look-ahead but the documentation is pretty solid too: http://pear.php.net/manual/en/pyrus.extending.installation.php